Over the last few days there has been a lot of uncertainty over what the Labour Party position will be when Parliament votes on whether, and how, the UK government should begin the process of leaving the EU. That lack of clarity obviously reflects deep differences in approach within the leadership and the wider parliamentary party.

It shouldn’t be like this. The decision that will need to be taken is one of the most important that the UK has ever faced. Now that the Conservative government has at last made clear its Brexit objectives, Labour must come up with a coherent – and democratic socialist – response if we are to have any credibility as a serious opposition party.

And we should leave no doubt that Theresa May’s approach is one that we must reject in its entirety. If Labour has ‘red lines’ which it has said the government must not cross, but the government then breaches them, then Labour must vote against those plans. Making a fuss, but then at the end of the day voting to trigger Article 50 in such a way as to allow the government to negotiate as it wants, would make Labour look absurd.

My view is that given the narrow majority in the advisory referendum, and the way in which it becomes clearer every day that Brexit was sold on a false prospectus, the UK should not start the Article 50 process but seek to negotiate further changes in the EU to reflect those concerns. I suspect most other EU states would welcome that.

But if Labour is prepared to vote to start the Article 50 process, then it should seek to amend the government’s proposals to make it clear that it is only authorised to negotiate with the EU on the basis of the UK staying in the single market, and keeping the progressive EU-wide policies on issues such as environmental protection, and workers’ and social rights. It ought to be possible to achieve a Parliamentary majority for that, from Labour, SNP, LibDem, smaller parties and some pro-EU Tories. If such an amendment is lost, then Labour should vote against giving the government the go ahead to start the Article 50 process.

To give the government the freedom to pursue its vision of the UK as an offshore tax haven would be a total betrayal of Labour’s values, principles, and history. It would also likely to be electoral suicide. Hardly any votes would be won back from UKIP or anti-European Tories, but millions more voters in England would be likely to move to the LibDems or the Greens, and in Scotland, a few more votes would be lost to the SNP. We should not need to be discussing whether Jeremy Corbyn would be allowing a free vote on the issue; what we want is Jeremy Corbyn is to be making it clear that Labour will vote against giving the go-ahead to the Tory Brexit plans.